He also went on to congratulate Jimmy Fallon, who is replacing him as Tonight Show host in spring 2014, news that NBC officially confirmed earlier Wednesday.

"He is a hell of a guy! He's going to do a great job. I just have one request for Jimmy: We've all fought, kicked and scratched to get this network up to fifth place. Now we have to keep it there! Jimmy, don't let it slip into sixth! We are counting on you."

He also quipped that he's accepted a new position as the "head basketball coach at Rutgers University" (Mike Rice was fired by the university Wednesday after a video surfaced in which he was seen shoving and grabbing players and throwing basketballs at them.) and joked that rumors already have begun about Fallon's Tonight Show replacement.

"NBC says in five years, they plan to replace Jimmy with Justin Bieber," he said. "They are moving too quickly!"

Meanwhile, on his own show, Late Night host Jimmy Fallon thanked Leno for being "gracious" as well as his own staff. He also addressed the news in his monologue.

"Hello! Welcome! This is Late Night With Jimmy Fallon -- for now," he said. "You guys probably heard the news -- I’m going to be taking over The Tonight Show next February! But don't worry. Until February, our focus is right here on whatever this show is called."

David Letterman also made jokes about the late-night shake-up in his monologue and even did a Leno-themed top 10 list on Wednesday night's Late Show.

"I got a call from my mom today," he said. "She says, ‘Well, David, I see you didn’t get The Tonight Show again.’ ”

NBC confirmed the news about its late-night shake-up Wednesday, a month after The Hollywood Reporter revealed that the network was preparing an exit plan for Leno. THRreported Tuesday that Fallon had signed the Tonight deal and that Saturday Night Live stalwart Seth Meyers is being eyed as his Late Night replacement.

When Fallon takes over, Tonight Show will return to 30 Rockefeller Plaza in New York, where it will be executive produced by Fallon's former Saturday Night Live bossLorne Michaels.